Power driven medical injector syringe with electromagnetic coupling means



United States Patent [72] Inventors Heinrich Reich Wurenlos, Aargau,Switzerland; Jean Paul Stucky, Zurich, Switzerland Appl. No. 650,084Filed June 29, 1967 Patented Aug. 11, 1970 Assignee Contraves, A. G.

Zurich, Switzerland Priority June 30, 1966 Switzerland No. 9508/66 POWERDRIVEN MEDICAL INJECTOR SYRINGE WITH ELECTROMAGNETIC COUPLING MEANS 10Claims, 6 Drawing Figs.

US. Cl l28/2.05, 128/218, 222/333 Int. Cl A6lb 5/02, A61m 5/20 Field ofSearch 128/2, 2.05,

Primary Examiner- Dalton L. Truluck Attorney- Michael S. StrikerABSTRACT: An arrangement for injecting a contrast medium into the heartof vascular system of a patient, in a precisely controlled fashion. Themovement of the injecting syringe is driven by a constantly rotatingmotor, via an electromagnetic coupling. The coupling connects thesyringe piston to the drive shaft of the motor so that when the couplingis actuated by current flowing through the coil of the coupling, thesyringe is made to respond immediately to such actuation. The speed ofthe injection of the contrast medium or medical fluid is closelyregulated through the action of the coupling and the driving motor.Indicating means are provided whereby the amount of fluid retainedwithin the syringe is continuously indicated. When the amount of fluidwithin the syringe drops below a predetermined level, actuation of thesyringe is immediately inhibited. Control circuitry provides a signalwhen the number of injections that have taken place correspond to apredetermined quantity, and a push-button assures that the injection ofthe medical fluid cannot take place unless the latter is depressed.

Patented Aug, 11, 1970 Sheet Patented Aug. 11,1970

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FIG.6

HE/A E/CH 25/6/4 JEAN PAUL. STUCKV POWER DRIVEN MEDICAL INJECTOR SYRINGEWITH ELECTROMAGNETIC COUPLING MEANS BACKGROUND OF ,THE INVENTION It iswell known in the art that for purposes of performing X- ray examinationand investigations of the circulatory systems of patients, a fluid inthe form of a contrast medium must be injected into the vascular system.The tolerable amounts of fluids which may be injected are limited andare as follows:

The maximum dosage for adults is 1.5 mLIkg. of body weight. Forchildren, the maximum dosage is 2-3 mL/kg. of body weight.

Since a pulsed flow prevails in the circulatory system and in the heart,the injection process must be extremely rapid in order that sufficientconcentration of contrast medium is present at a particular location,for diagnostic purposes.

During heart examinations and especially when large volumes of injectingfluids are involved, very severe technical requirements must be adheredto. Thus, the injection speed must be extremely large, the pressure risemust be rapid, the injection must be performed with sharply definedbeginning and end points, the injected volume as a function of time mustbe precisely monitored, and the total amount of fluid that has beeninjected must be closely controlled at any instant.

Recent investigations have shown that during the contraction orevacuation phase of the heart, it is not desirable to inject thecontrast medium into the vascular system. Thus, during this period ofthe contraction phase, the injected contrast medium is simultaneouslyejected and becomes thereby useless from the diagnostic point of view,since the information that was to be derived therefrom cannot berealized. Furthermore, due to the reduction in the volume, within theheart, due to the contraction phase, it is dangerous to inject into theheart or the vascular system. Accordingly it is of advantage to injectinto the heart intermittently only when the filling phase takes place,corresponding to normal hemoclynamic techniques. When this technique isobserved whereby the injection of the contrast medium is performedintermittently only during the filling phase of the heart, considerablymore information is made available of the heart condition, and with lessdanger and disturbance to the system of the patient. However, as aresult of applying this particular examination technique, asubstantially shorter period of time is available for the injection.Accordingly, the injection must be accomplished with a rapid pressurerise, precise regulation of the timing and volumetric parameters of theinjection impulse as a function of the electro-cardiogram, as well asclose programming of the injection apparatus. Conventional injectionapparatus for the contrast medium, have an injection piston driven by anelectric motor which may be operated as an onoff unit. However, it hasbeen found that such conventional apparatus cannot respond sufficientlyrapidly to an electrical signal for controlling the on-off operation ofthe motor. Furthermore, the conventional apparatus has the disadvantagethat a time lag of 0.3 to 0.7 second prevails between the instant thatan electrical control signal for operating the motor is transmitted andthe instant that the injection piston acquires the necessary designatedspeed. This disadvantageous condition results principally from the factthat in the conventional apparatus the electric motor drives theinjection head through a screw mechanism having a longitudinally movablescrew spindle. With such design considerable mass is inherentlyaccelerated or decelerated commensurate with the on-off operation of themotor, and this is responsible for the large delays in response. Thesolution to the problem does not reside in providing a larger motor withgreater power capabilities, because such a modification in the design ofthe apparatus would produce an unmanageable system due to the heavierconstruction that would be required in all aspects of the design.

In other conventional apparatus for injecting medical fluids, theinjection is performed through the action of a pneumatic cylinderoperating in conjunction with a control valve. These pneumatic designsderive the air from pressurized storage tanks which will last only for arelatively few operating hours. At the same time the time lagsassociated with the motion of the injection piston are even larger thanthose encountered in the systems using electrical motors.

With these viewpoints in mind, the present invention is of specialadvantage because it accomplishes the injection mo tion in a rapid andsharply defined on-off operation.

One object of the present invention is to provide an injection apparatusin which the speed of the injecting piston may be preselected. Thepresent invention provides, moreover, for a continuously moving electricmotor which, upon the application of a control signal, drives thesliding mechanism of the injection piston within the prescribed timeinterval and at the preselected speed. It is also an object of thepresent invention that upon transmission of the control signal, of thedesignated speed of the injection system should be attained within msec.

The present invention accomplishes the preceding objects by providing ascrew spindle driven as a result of a motor and a nut in mesh with thescrew spindle. The screw spindle is supported by a spindle retainer.Between the latter and the nut, resides an electromagnetic couplingcontrolled by a control signal. The design is such that in one state ofoperation the spindle retainer is secured to the nut to provide for thedesired translational motion of the spindle. In another state ofoperation translational motion of the spindle is inhibited.

In accordance with another embodiment of the present invention, ahydraulic operating mechanism is connected to the injection piston. Amotor driven pump sets into motion a hydraulic fluid against pressure. Avolume regulating valve regulates the flow of the fluid through thehydraulic system. In one state of a hydraulic control valve, operated bya control signal, the hydraulic fluid is returned to the intake of thepump via a hydraulic resistance. In the other state of the hydrauliccontrol valve, a differential piston is operated whereby the injectionpiston is translationally moved in the desired manner.

It is very useful, when possible, to monitor continuously the positionof the injection head for the purpose of determining the volume ofcontrast fluid available. Thus, when the volume of fluid remainingwithin the syringe drops below a predetermined level, the injectionapparatus may be immediately switched off. lt is also desirable that anyinjection phases take place only when a pushbutton is maintaineddepressed by the responsible physician in charge. ln this manner thephysician can discontinue the injection operation at any instant by therelease of the pushbutton. It is of special significance when thecontrol signal for operating the injection apparatus is regulated as afunction of the operation of the heart, by being associated with theelectrocardiogram. Thus, operation of the injection apparatus can beinhibited whenever a spike signal appears on the electrocardiogram. Insuch an arrangement the maximum duration of the injection phase as wellas the number of injection impulses may be closely regulated. The volumeof contrast medium injected into the patient is, furthermore, alsolimited. After successful injection of a predetermined volume ofcontrast medium, a control signal may be transmitted for the purpose ofautomatically switching on X-ray examination apparatus.

SUMMARY OF THE lNVENTlON A medical injection apparatus having a syringewith a movable piston therein for injecting a predetermined quantity offluid into the vascular system of a patient. The piston of the syringeis moved translationally through the action of a continuously operatingmotor. The motor as well as the piston of the syringe are driven at apredetermined speed. Intermittent operation of the syringe piston isaccomplished through an electromagnetic coupling connecting the pistonwith the continuously operating motor. A control signal transmitted tothe electromagnetic coupling connects or disconnects at will the syringepiston drive from the electric motor. The on-off operation of theintermittent drive is such that extremely rapid response to theelectrical control signal is realized. The time interval during whichthe injection phase takes place is precisely regulated, as well as thespeed of injection. The volume injected into the patient as well as thenumber of injection impulses are also continuously monitored. Safetydevices are included to minimize any danger to the patient as a resultof the injection processes.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an elevational view of thesupporting structure of the injection apparatus;

FIG. 2 is a plan view of the injection apparatus of FIG. 1;

FIG. 3 is a functional electrical schematic diagram, and shows themanner in which the action of the injecting syringe is controlled;

FIG. 4 is a timing diagram of the signal flow through the electricalcircuits and controlling apparatus in FIG. 3;

FIG. 5 is a cross'sectional elevational view of a screwoperated drivingmechanism for securing on-off operation of the syringe; and

FIG. 6 is a functional schematic diagram of a hydraulic system, andshows another embodiment for controlling the action of the syringehydraulically.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing and inparticular to FIGS. 1 and 2, a movable carriage A carries a supportingmember B for the injection apparatus and its associated controlequipment. The syringe is denoted by C. It is actuated by a drivingmechanism located within a housing D having an interchangable supportingarm D, for the purpose of gripping the syringe. The housing D alsocontains control and switching mechanisms which have their operating andadjusting members arranged on the operating panel D An electronic unit Dis connected to the housing D, and has its operating members on thefront panel D20. By means of the clamping screw 8., all parts secured tothe housing D may be rotated about the horizontal axis of FIG. I, or thevertical axis of FIG. 2. Thus, these parts may be adjusted andpositioned in any desired manner. The upright position of the supportingarm D shown in FIG. 1, serves for the purpose of removing the air fromthe syringe C. In this regard, the piston head is set for executing slowfilling and injection motions. In order to drive out all air bubblesthat may remain in the syringe, it has been found useful to provide asmall electrical vibrator C: at the supporting arm D in the vicinity ofthe syringe C. The principle governing the functional operation of theapparatus ofFIGS. land 2 is shown in FIG. 3.

In accordance with FIG. 3, the injection apparatus serves the purpose ofinjecting a contrast medium into the heart and hence the vascular systemofa patient H lying on a table E exposed to X-ray apparatus F. Theobservation apparatus is denoted by G. In accordance with thearrangement, the functions of the heart of the patient H arecontinuously monitored by the cardiogram I, so that a signal in the formofi appears as in FIG. 4. The signal i is also applied to a commonlyknown Schmitt trigger circuit J which provides a trigger signalj thathas a duration which is at least as long as the duration of the spikesin the signal i. The Schmitt trigger circuit is actuated by themonitoring signal i. On the basis of the manner in which the cardiogramapparatus I is connected to the body of the patient, the contractionphase of the heart may also be represented by an electrical signalwhich, for example, corresponds to the signalj resulting from thetrigger circuit J.

A push-button K having two switching contacts K and K are provided toenable the attending physician to release the injection mechanism and toblock it as desired. Thus, when the push-button K is depressed, theinjection mechanism becomes operative, whereas it remains in theinoperative state at all other times. The signal resulting from thedepression of this push-button K, is designated by k in FIGS. 3and 4. Amultivibrator or similar timing circuit L capable of providing a timedelay t supplies binary signal 1 upon the rise of the trigger signal j.After the elapse of the time interval t,,, the binary signal I ceases.

The signal 1 is applied to a second timing circuit M which may be setfor maximum time t,,, for the purposes of determining the maximumduration of a signal m. The circuit M becomes operative when the signal1 ceases, and becomes inoperative, on the other hand, when the signal 1rises. This operation of the circuit M is, at the same time,accomplished no later than the elapse of the maximum time interval t,,,.As a result, the volume of the contrast medium injected, is limited to aquantity below a predetermined maximum. Fundamentally, it is possible toprovide that the signal m be directly applied for the purpose ofactuating the movement of the syringe piston C,.

A driving mechanism for the syringe is denoted by N and shownschematically in FIG. 3. This driving mechanism includes an electricalmotor N, which is connected to the power supply by means of the switchNu. The speed of rotation of the motor for the purpose of regulating thevolume injected, may be adjusted in a fully continuous manner throughthe potentiometer N Speed control means are commercially available forswitching control of the electric motor to an exceptionally low speedrange. These can be used to fill and empty the syringe for the purposeof removing the air therein. The motor N operating at a predeterminedspeed, drives the actuating mechamism N2 for the injection of pistonhead C with corresponding speed. The magnetic coil N20 serves as theon-off switching mechanism for the motion of the injection head, throughmeans of the control signal 0. Concrete examples of the drive Noperating in conjunction with a continuous rotating motor N, are givenin FIGS. 5 and 6.

In FIG. 3 is also shown a mechanism to which the motion of the injectionpiston is transmitted by way of a flexible tension member 0 secured to aspring 0... The flexible tensile member 0 passes over a volumeindicating disk 0 and a volume selecting member 0 The scale and theindicating disk 02 provides an indication, therefore. of the volume ofcontrast fluid within the syringe. The volume selector O is providedwith a cam projection 0 which acuates an electrical switch 0 Thus, theswitch O is retained in the open state when the volume of fluid withinthe syringe is below a predetermined limit V (FIG. 4). Since the switchOm is connected in series with the switching coil N3. the injectionmotion can take place only when the contents within the syringe areabove the predetermined limit V,,. In the simplest manner. the gap at Pmay be bridged so that a positive voltage may be applied to theactuating coil N when the switching contact K is closed, as well as theswitch 0;". Thus, by depressing the push-button K the syringe C may beoperated until the minimum volume therein is attained.

In accordance with FIG. 3, the bridge P is connected to the output ofalogical AND gate O which has, as one of its input signals, the outputofthe timing circuit M. The second input R of the gate Q is realizedfrom a register R into which may be inserted a maximum quantity r,, as,for example, five injection impulses. The register is set back by oneunit whenever the actuating coil N receives a new current impulse 0. Assoon as the predetermined quantity r, of injection impulses has beenattained, and the register R is thereby in its zero state, the signal ris switched off so that further releases of injection impulses is notpossible.

From the preceding description of FIG. 3, it may be seen that theactuating coil N20 can receive operating current signals 0, only underthe following conditions:

a) The push-button K must be depressed.

b) No signal 1 must be present, implying that the injection motion isblocked for a predetermined time interval t,, beginning from the instantthat the spike on the cardiograph i begins to rise.

c) The duration of the injection period cannot exceed the predeterminedmaximum value t,,,.

d) The maximum number of impulse signals r, on the register R, cannot beexceeded.

e) The minimum residual quantity v,, inserted by way of the residualregister 0 must be exceeded.

in order that the speed of injection corresponds to the predeterminedmotor speed, the injection flow as well as the injection impulse offluid volume is limited through the limiting of the duration t,,,.

Through the use of similar auxiliary equipment, it is possible to derivea signal 0 which actuates, for example the X-ray apparatus G or partsthereof, when apredetermined quantity of contrast medium has beeninjected.

in accordance with FIG. 5, the driving shaft of an electric motor 1rotatable at a predetermined speed, drives a gear train 12 via thecoupling 11. The driven gear of the train 12 meshes with the peripheralgeared surface of a planetary gear 13. A plurality of planetary spindles14 are freely mounted within the planetary gear 13 so that they aremovable about the central axis of the planetary gear. Thecircumferential ribs of the planet spindles 14 mesh with a screw threadof a main screw spindle 15 which is coaxial with the gear 13. Theplanetary gear train acts upon the screw spindle 15 in the form of ascrew nut, but with lower frictional losses. As long as the main spindlerotates with the same angular speed as the gear 13, no axialdisplacement takes place with respect to this main spindle. Upon brakingthe rotational motion of the main spindle, an axial displacement of thespindle 15 takes place in the direction indicated by the arrow P15. Thisaxial displacement occurs most rapidly for complete blocking of therotational motion of the main spindle 15, for a predetermined speed ofthe gear 13.

The main spindle 15 is securely keyed by means of the key 16 to aspindle carrying sleeve 17. The keying arrangement is such that the mainspindle 15 is slidable within the sleeve 17 but not rotatable withrespect thereto. The spindle supporting sleeve 17 is, as the gear 13,rotatably supported in stationary members 18a and 18b of a housing andcoaxial to the main spindle 15.

Through a friction coupling represented by a disk spring 19, the gear 13is coupled to the flange portion 170 of the spindle supporting sleeve17. The hub 17] of the spindle supporting sleeve 17 is keyed to the disk20 of a magnetically actuated coupling including the magnetic coil 200.The keying arrangement is such that whereas relative rotation betweenthe key members is inhibited, they may slide axially with respect toeach other. When the coil 200 is in the de-energized state shown, thedisk 20 rotates with the sleeve 17 which, on the other hand, is drivenby the gear 13. When the coil 200 becomes energized, the disk 20 isdrawn towards the coil 200 and tends toward the stationary housingportion 18a. As a result, the rotational motion of the disk 20 isinhibited. Beginning from this instant, the spindle retaining assembly17- 170-171 is stationary, and a corresponding axial motion of the mainspindle 15 is forced in the direction of the arrow P When the currentthrough the coil 200 ceases, the gear 13 rotates against the sleeve 17,through the frictional coupling 19. As a result, the main spindle 15 isrotated with the same speed of the gear 13 and the axial motion of thespindle 15 in the direction of the arrow P ceases. Substantially, notime lag prevails with regard to the transfer of motions of the spindle15 between the rotational motion and the axial sliding, as a result ofthe current through the coil 200. Through the arrangement of the presentinvention, involving the screw thread drive, a very well defined yes-notransfer device is obtained for the spindle sliding motion. Thus, whenthe current in the coil 200 is switched to a different level, 90% of thecorresponding motion of the spindle is realized within 0.01 seconds.

A hydraulic embodiment for driving the mechanism whereby the contrastmedium is injected, is shown in FIG. 6. This arrangement includes anelectrical motor 30 which may be connected to a current supply 32 bymeans of a switch 31. The motor 30 drives, by means of a coupling 34, ahydraulic pump 35. The latter takes a hydraulic fluid working mediumfrom a storage tank 36 and forces it into a pressure line 37. A safetyvalve 38 allows the pressurized fluid to return to the storage tank whenthe pressure in the line 37 exceeds a predetermined value. A three-wayregulating valve 40 allows a predetermined volume of fluid to flow inthe line 41, as a function of time. Any excess volume of fluid istransferred to the branch line 39. An electromagnetic valve 420controlled by an electrical coil 42, connects the fluid line 41 with thefluid line 43 leading to a throttle member 44 connected to the returnflow line 39. When current is permitted to flow through the coil 42 bymeans of the closing, for example, a switch K, the fluid line 41 nolonger communicates with the fluid line 43 leading to the throttlearrangement 44. Instead the fluid line 41 is, under these conditions,connected to the fluid line 45. The latter leads to a hydraulic cylinder47 containing a differential piston 46. The same pressure prevails onthe left surface of the piston 46 because this side of the piston is fedwith fluid from the line 41a. However, the force is greater upon theright surface of the piston 46, and as a result the injection piston Cof this syringe C is actuated and injects the contrast 7 medium into thepatient H.

The speed of motion of the pistons 46 and C is precisely proportional tothe setting of the volume regulator 40 which regulates the flow into theline 41. As long as the return valve 48 between the flow lines 45 and 39is maintained manually open, the piston 46 is driven to the right,through the flow lines 41 and 41a, for the purpose offilling the syringeC.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofmedical injection apparatus differing from the types described above.

While the invention has been illustrated and described as embodied inmedical injection apparatus, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

We claim:

1. A medical injection apparatus comprising, in combination, a syringehaving a movable syringe piston for injecting medical fluid; drivingmeans for driving said piston within said syringe; a continuouslyoperating energy source for operating said driving means at apredetermined speed; an electromagnetically operated coupling connectingsaid driving means with said energy source upon application of a controlsignal to said coupling, whereby said syringe piston moves at saidpredetermined speed immediately upon actuation of said coupling by saidcontrol signal, said syringe piston becoming stationary immediately uponthe release of said coupling by said control signal; push-button meansfor transmitting said control signal to said coupling means only whensaid push-button means is depressed; and delay means for delaying saidcontrol signal to said coupling by a predetermined time interval.

2. The medical injection apparatus as defined in Claim 1 including meansfor regulating the maximum duration of injecting said fluid within saidsyringe.

3. The medical injection apparatus as defined in Claim 2 includingregulating means for limiting the maximum number of injections to beperformed by said syringe.

4. The medical injection apparatus as defined in Claim 3 includingsignal emitting means for emitting a signal when a predetermined amountof fluid has been injected by said syringe.

5. A medical injection apparatus comprising, in combina' tion; a syringehaving a movable syringe piston for injecting medical fluid; drivingmeans for driving said piston within said syringe; a continuouslyoperating energy source for operating continuously said driving means ata predetermined constant speed; actuating means linked to said drivingmeans and continuously driven at said constant speed when in a freelyoperating state; and an electromagnetically operated coupling connectedto said actuating means for changing the speed of said actuating meanswhen engaged by said coupling upon ap plication of a control signal tosaid coupling, whereby said driving means moves said syringe piston at apredetermined constant speed immediately upon actuation of said couplingby said control signal and change in speed of said actuating means, saidsyringe piston becoming stationary immediately upon disengagement ofsaid actuating means from said coupling through termination of saidcontrol signal, said actuating means returning to said freely operatingstate upon termination of said control signal.

6. The medical injection apparatus as defined in Claim 5 wherein saiddriving means comprises a threaded spindle coupled to said piston formoving the same, said actuating means comprising a threaded sleeveretaining said spindle and rotatable with respect thereto; and arotatable nut whereby said spindle sleeve is connected to said nut inone state of said coupling. and motion of said sleeve is inhibited inthe other state ofsaid coupling.

7. The medical injection apparatus as defined in Claim 5 includingindicating means for continuously indicating the position of saidsyringe piston for providing an indication of the amount of medicalfluid within said syringe.

8. The medical injection apparatus as defined in Claim 7 includingvolume selecting means for selecting the minimum volume of fluid to becontained within said syringe, whereby' said syringe piston is inhibitedfrom moving when the medical fluid within said syringe is below thepreselected volume.

9. The medical injection apparatus as defined in Claim 5 includingpush-button means for transmitting said control signal to said couplingmeans only when said push-button means is depressed.

10. A medical injection apparatus comprising, in combination, a syringehaving a movable syringe piston for injecting medical fluid; drivingmeans for driving said piston within said syringe; a continuouslyoperating energy source for operating said driving means at apredetermined speed; an electromagnetically operated coupling connectingsaid driving means with said energy source upon application ofa controlsignal to said coupling, whereby said syringe piston moves at saidpredetermined speed immediately upon actuation of said coupling by saidcontrol signal, said syringe piston becoming stationary immediately uponthe release of said coupling by said control signal, said driving meanscomprising: a hydraulic cylinder and piston for moving said syringepiston at a predetermined speed; a motor driven hydraulic pump forforcing fluid into said hydraulic cylinder; a fluid regulating means forregulating the amount of fluid admitted to said hydraulic cylinder; ahydraulic control valve for diverting in one state the fluid from saidcylinder and passing another state said fluid to said cylinder formoving said syringe piston to inject medical fluid; and hydraulicthrottle means connected to said hydraulic control valve for receivingthe fluid diverted from said hydraulic cylinder and transferring thediverted fluid to the intake of said pump whereby said hydraulic pistonmoves said syringe piston when said hydraulic control valve passes fluidinto said hydraulic cylinder.

